Voice minutes were flat in 2012, the industry group said

U.S. mobile networks carried 69 percent more data traffic in 2012 than in the prior year, but roughly the same number of voice minutes and fewer SMS messages, according to the industry group CTIA.

The findings came from a semi-annual survey by the organization, which represents the nation's mobile operators. The results released Thursday covered the full year 2012.

Data traffic bounded past 1 trillion megabytes in 2012, rising from 866.8 billion megabytes in 2011 to 1.468 trillion megabytes last year, CTIA said. Other results show factors that probably helped to drive that growth. For one thing, the number of active smartphones (and "wireless-enabled PDAs") grew 36.4 percent, while even more data-hungry wireless-enabled devices, such as tablets and laptops, grew by 10.2 percent.

The total number of subscriber connections crept up by 3.3 percent to 326.4 million, more than the number of people in the country: Wireless penetration in the U.S. was 102 percent at the end of last year, according to CTIA.

However, the use of SMS declined, with 2.19 trillion text messages sent and received in 2012, down 4.9 percent from 2.3 trillion a year earlier. That may not mean consumers are sending fewer short text messages to each other but that more are using so-called "over the top" messaging services such as Skype and WhatsApp, which don't count toward SMS traffic totals. Meanwhile, SMS's multimedia cousin, MMS, grew by 41 percent to 74.5 billion messages sent and received. That's good news for carriers, though MMS use is still on a far smaller scale.

Subscribers spent more time talking on the phone in 2012 than in 2011, but only by a bit. Minutes grew by 0.2 percent to 2.2999 trillion.

The group and its carrier members have used growth in mobile data for years to support calls for more radio spectrum being opened up for mobile services. But in its press release announcing the latest survey results, the group put the spotlight on how much carriers are investing in their networks: $30.1 billion in 2012, up 19 percent from the prior year.

That's the most the carriers have spent in any year since the survey began in 1985, and it comes out to US$94 per subscriber, the group said. That sum also dwarfs the level of mobile network investment around the world, which averages $16 per subscriber, according to CTIA.